Question

A speeding motorcyclist sees traffic jam ahead of him. He slows down to $36km/hour$. He finds that traffic has eased and a car moving ahead of him at $18km/hour$ is honking at a frequency of $1392Hz$. If the speed of sound is $343m/s$, the frequency of the honk as heard by him will be :

• A. $1332Hz$
• B. $1372Hz$
• C. $1412Hz$
• D. $1454Hz$

Answer 1

The correct option is C $1412Hz$

Appearent frequency heard by the observer is
$f^{\prime }=f_0\left(\frac{V-V_0}{V-V_S}\right)$
$f^{\prime }=\left(1392\right)\left(\frac{343-(-10)}{343-(-5)}\right)=1412Hz$